hildebrandt



United States Patent EXPANDING: TYPE MOMENTUM PELLET IMPACT; DRILLINGAPPARATUS Alexander B. Hildebrandt,Tulsa, 0kla.,.assignor to EssoResearch and Engineering Company, a corporation of Delaware ApplicationOctober 28, 1952, Serial No. 317,318

4 Claims. (Cl. 255;61)

This invention concerns a novel'form of a drill bit for the drilling ofbore holes in the earth. The apparatus of this invention is ofparticular application in drilling for petroleumoil. The inventionembodies the principles of pellet impact drilling in which a largenumber of hard dense spherical pellets are entrained in a high velocityfluid jet so as to be forcefully impinged against an earth formation tobe drilled.

The invention particularly concerns the manner in which these pelletsare recirculated in the immediate vicinity of the drilling zone. Inaccordance with this invention a particular type of shroud or cage isprovided to cause the captive deflection and're-circulation of thepellets adjacent the drilling zone so as to redirect the pellets intothe fluid jetemployed. A pellet deflecting cage is used incorporatingmeans to expand the cage, during drilling, to the gauge size of-the borehole. When drillin is discontinued the pellet deflector cage is of acharacter permitting contraction to a diameter less than that of thedrill hole to facilitate removal of the drilling apparatus from the borehole.

It has recently been discoveredthat a remarkably effective drillingaction can be achieved bya basic innovation in drilling techniques. Thecopending patent application, Serial No. 268,873 filed for Philip S.Williams, on January 29, 1952, entitled Pellet Impact Drilling Methodand Apparatus, sets forth the basic principles of this drillingtechnique. In-accordance-therewith a stream of fluid is pumped from thesurface of the earth through a tubular member to a jet nozzle assemblysuspended thereby in a bore hole. While a variety of jet nozzleassemblies may be employed, these assemblies are so arranged as to causethe forceful ejection-of a directed high velocity jet of fluid. Thenozzle assembly is of a nature to permit entrainment of a multitude ofpellets in this fluid jet. Entrained in the fluid jet, the pelletsattain a high kinetic energy so that on impingement against the bottomof the bore hole, percussion and fracturing forces cause a drillingaction. The pellets to be employed are smooth, non-abrasive, sphericalpellets having a diameter of about /8 of an inch to one inch. Hard,tough metallic alloys are preferably employed.

In considering this basic drilling technique it becomes important toprovide a suitable and effective manner of securing continuousrecirculation of the pellets in the fluid jet. Thus means are requiredto carry pellets upwardly after impact and to permit the pellets to bereentrained in the fluid jet. In this connection it would appearimpractical to consider circulating the pellets through any substantiallength of the bore hole. It is clearly of the greatest practicalimportance to enable recirculation of the pellets in the immediatevicinity of the drilling zone. This serves to conserve the energyrequired and to increase the effective density of the pellets in thedrilling zone while permitting use of a smaller number of pellets.

In the patent application referred to, setting forth the basicprinciples of pellet impact drilling, one. manner of ice securing thedesired recirculation of the pellets is disclosed. This method requiresconfiguration of the jet nozzle assembly so as to provide a gravitysettling zone above the assembly, in which the pellets may separate.from the drilling fluid so as to.settle in a recirculation channelcommunicating with the fluid jet. This invention is in part directed toan improvement of. this gravity separation technique, particularly inproviding means to effectively employ momentum of thepellets for,effective re-entrainment in the jet.

The basic principle employedin the method and awe: ratus of thisinvention is to provide a deflecting surface in the annular space abovethe jet assembly between the drill pipe and the bore hole.; Thisdeflecting device is so arranged as to effectively block passage of thepellets upwardly while permitting passage of drilling fluidandpulverized earth formation. Consequently the deflector serves toseparate and, at least in part, to redirect the pellets towards theentraining fluid jet for recirculation.

To provide a deflector of the required character it has been founduseful to employ a dependent shroud suspended below the nozzle assemblyemployed in propelling the pellets. This shroud can constitute arigid-metallic sleeve element having an outer diameter equal. to thegauge of the bore hole drilledby the pellets. The sleeve is preferablyjoined to the jet assembly so as to provide a curved deflecting surfacefor pellets. In addition to these features the sleeve or shroud isperforated at least atthe upper portion to permit the upward passage ofthe drilling fluid while blocking the passage of pellets upwardly. Inthis arrangement pellets ejected by the jet assembly are directedagainst the bottom of the bore hole to secure drilling action. The outerandupward circulation of the entraining drilling fluid causes thepellets to be directed upwardlyalong the inner surface of the sleeve. Inthe upward passage of the pellets along the sleeve, the pelletsencounter the curved deflecting surface referred to so as to beredirected into the fluid jet for continuous cyclic drilling action.

While the type of a rigid shroud element described has been foundeffective in controlling recirculation of pellets during drilling,difficulties have been encountered in removal of this apparatus from aborehole. By-the nature of the shrouded pellet impact drillingapparatus, the shroud will andmust fitcloselyin the borehole duringdrilling. Consequently when it becomes. necessary. to remove this drillfrom the bore hole the possibility of jamming exists and it may becomediflicult to extract the drill from certainformations.

it istherefore the principal object ofthis invention to provide ashrouded pellet impact drill in which the shroud can assume one of twopositions. In. a first contractedposition, assumed by the apparatus whendrilling has been. discontinued, the shroud of the apparatus. ismaintained ata smaller diameter. than the bore hole drilled. by theapparatus. In. a second drilling position of the apparatus, the shroudis. maintainable in an expanded position equal to the gauge size of theborehole drilled. This expansible: featureof the shroud greatly improvesthe practical utility of the drilling apparatus and eliminates problemsotherwise encountered in withdrawing the apparatus from the bore hole.

The apparatus by which, these objectives are accomplished ischaracterized by useof a shroud or pellet deflecting cage which is;segmented. Thus the sleeve or shroud employed may be, cut along verticalplanes. so that the shroud; includes some 10,. to, 20 individualsegments. Each of thesev segments is dependent; from a supporting.member which may constitute the nozzle. as sembly used for propellingthe pellets. The individual segment r nge to the uppo t ng: mem e o m ye. flexibly fi ed. there o... so. as perm t: mited exp nsion O andcontraction of the lowermost portion of the shroud. In order to securethe positive expansion of the shroud segments, hydraulic means areemployed to forcefully expand the shroud members to the extendeddrilling position when drilling fluid is pumped through the nozzleassembly for drilling operations.

The nature of this invention may be fully understood by reference to theaccompanying drawings in which:

Fig. l diagrammatically illustrates in a cross-sectional elevationalview one form of the apparatus of this invention employing articulatedshroud segments adapted to be expanded to drilling position by thehydraulic force exerted on the primary nozzle of the jet assembly.

Fig. 2 is a sectional view of Fig. 1 along line IIll of Fig. 1particularly showing the manner in which the secondary nozzle issupported by the segmented shroud.

Fig. 3 shows an alternative form of the present invention incross-sectional elevational detail particularly adapted for use offlexible shroud members.

Finally Fig. 4 shows a cross-sectional view of Fig. 3 L

along line lVlV to particularly show the segmented shroud members.

The apparatus of Fig. 1 is illustrated in drilling position within abore hole 1 drilled in the earth. The drilling apparatus is held in thebore hole on a drill string or tubular member 2. A plurality of shroudsegments 3 are hinged to the lower termination of the tubular support 2.Thus, for example, each of the shroud segments may be held in pivotalrelation to support 2 by means of pivot pins 4 passing through lugs ofeach shroud segment and fixed to tubular support 2. The shroud segmentsare maintained in closely spaced relation with each other.

Each of the shroud segments 3 carries an upwardly extending springextension 5 which bears against tubular support 2. The spring extensions5 bear against support 2 so as to urge the lower edges of each shroudsegment inwardly towards the center of the bore hole. Each of the shroudsegments 3 is provided with an inner exten sion adjacent the pivot 4which tapers inwardly and downwardly. These extensions are identified bynumeral 6 in Fig. l. A nozzle element 7 fitting within the lowerextension of tubular member 2 is shaped to mate with the taperedextensions 6. Thus the lower end of nozzle 7 tapers inwardly at itslower termination so as to bear against the inclined surfaces presentedby the extensions 6. From this configuration it is apparent that adownward force exerted on the nozzle 7 applies a cam or lever actionagainst the extensions 6 forcing each of the segments outwardly in thebore hole.

In addition to the elements described a number of inwardly extendinglugs 9 may be positioned on some of the shroud segments. As shown inFig. 2 four such inwardly extending lugs may be employed. These lugs areused to hold a secondary nozzle element 10 within the shroud concentricwith the primary nozzle 7. Thus the secondary nozzle 10 is equipped withan enlarged collar element 11 adapted to rest on the inwardly extendedlugs 9 of the shroud. The collar 11 of the secondary nozzle 16 has asufiicient diameter to permit the shroud segments to expand or contractwithin the range desired without permitting the secondary nozzle to dropdownwardly.

In order to limit the extended position of the shroud segments alimiting ring 12 may be positioned in an external circumferential recessformed by notches in each of the shroud segments. This limiting ringwill lie loosely in the circumferential recess when the segments are inthe contracted position. However, when the shroud segments are extendedby operation of the drill each of the segments will bear against thelimiting ring so as to maintain the lower termination of the shroud atthe desired gauge size.

In drilling with the apparatus described, during lowering of the drillto drilling position, drilling fluid is not circulated to the drill. Asa result the upwardly extending spring 5 associated with the segments ofthe shroud will act to maintain the shroud segments in contractedposition. This contracted position will be limited by contact of thelugs 9 against the secondary nozzle element 10. When the apparatus hasbeen lowered to drilling position and pellets 25 placed within theshroud element, drilling fluid is pumped downwardly through support 2.This drilling fluid is converted to a high velocity fluid jet on passagethrough the primary nozzle 7. Passage of the drilling fluid through theprimary nozzle applies a downward force on the primary nozzle forcingthe extension of the segmented shroud elements. The lever action of thenozzle on the shroud segments is controlled by design so that the normaldrilling fluid action on the nozzle will cause full extension of thesegments to the limiting position fixed by operation of the limitingring 12. The

iluid ejected from the primary nozzle 7 is directed downwardly to theenlarged secondary nozzle 10. In part due to the enlargement of thesecondary nozzle, an aspirating action is exerted tending to entrainpellets in the fluid jet. These pellets are carried with the fluid jetthrough the secondary nozzle and are accelerated therein so as to beexpelled forcefully against the bottom of the bore hole- The drillingfluid in its normal circulatory path carries the pellets outwardly andupwardly along the bottom of the bore hole. The pellets are aided in theupward circulation bythe taper 15 provided at the lower terminationofeach of the shroud segments. The pellets are then carried upwardly alongthe inner surfaces of the shroud elements. The inward curvature of theuppermost portion of the shroud elements provided by extensions 6directs the pellets inwardly toward the secondary nozzle. Here, asdescribed, the pellets are again entrained in the fluid jet forcontinuous drilling action. Drilling fluid is adapted to pass upwardlyin the bore hole however through the separation provided betweenadjacent shroud segments. If desired additional perforations may be cutin the shroud to ensure the free upward circulation of the drillingfluid while blocking passage of the pellets. The drilling fluid is thusenabled to pass upwardly to the surface of the earth in the bore holeannulus and may be recirculated downwardly through the tubular support2.

It is apparent that when drilling is discontinued, by stoppingcirculation of the drilling fluid, the spring members 5 will again forcethe segmented shroud to its contracted position to enable ready removalof the apparatus from the bore hole. T o secure the desired advantagesof this provision, only limited extension of the shroud elements isrequired. Thus it is not ordinarily required for the shroud to expandmore than about /2" in diameter in order to fulfill the objectives ofthe invention.

The apparatus illustrated in Figures 3 and 4 is similar in nature to theapparatus described. For this reason corresponding elements areidentified by similar numerals. Again in the apparatus of these figuresthe shroud constitutes a number of segmented elements 3. These segmentsare not hinged as in the embodiment of Figure l, but instead are rigidlyfastened to or constitute a continuation of the tubular support member.Thus the tubular support member and the shroud member may be an integralunit and the shroud segments may be constructed by cutting a pluralityof vertical slots 18 in the shroud body, and extending each of the slotsto the region designated by reference numeral 19 in the lower end of thetubular support portion of the apparatus. In Figure 3 the verticalsection has been taken through one of the slots on the right-hand sideof the figure and through one of the segments on the left-hand side ofthe figure. The lower slotted section of the tubular memberwhichcomprises the upper portions 2% of each of the.

shroud segments may be sufliciently reduced in thickness so that each ofthe portions 20 will constitute a spring element which will be flexiblein nature. Consequently each of the shroud segments is adapted to moveoutwardly against the wall of the bore hole when force is appliedagainst the flexible elements 20 which normally bias the shroud segmentsinwardly with respect to the vertical axis of the apparatus.

Again a limiting ring 21 may be positioned in a circumferential recesscut in the shroud segments so as to limit the extended position of theflexible shroud segments. A secondary nozzle is supported within theshroud in the manner illustrated in Fig. 2, the enlarged collar element11 of the nozzle resting on the inwardly extended lugs 9 of the shroud.In view of the fact that the segmented shroud members extend upwardlyabove the region of the primary nozzle into the flexible extensions 20,it is necessary to employ an inner sealing sleeve 22 to prevent passageof drilling fluid through the slots between the segments. Sleeve 22 mayconstitute a cup-like member of flexible material such as rubber havinga central opening in the bottom of the cup for passage of fluid to theprimary nozzle. The upper portion of the cup 22 must extend withintubular support 2 above the juncture with the segmented shroud elements.In this arrangement the primary nozzle consists of a streamlined insertmember 23 inserted at the bottom of the sleeve 22 for the direction ofdrilling fluid into the secondary nozzle 10.

In this embodiment of the invention the cup-like sleeve member 22 playsan important part in the expansion of the shroud segments. Duringdrilling when drilling fluid is pumped through tubular support 2 a highhydraulic pressure will be exerted within the cup member 22. This forcewill cause the ballooning of the flexible cup member so as to forcefullyexpand the flexible portions 20 of the shroud segments. By this meansthe shroud is extended to the drilling position upon circulation ofdrilling fluid.

In other respects the apparatus and operation are of the nature formerlydescribed with respect to the apparatus of Fig. 1.

As described therefore this invention concerns a pellet impact drill bitemploying a segmented shroud for captive recirculation of the drillingpellets. The shroud segments are maintained in flexible relation withrespect to the support member of the apparatus so as to permit outwardextension of the shroud segments at the lower termination of the shroud.For this purpose, as described, the shroud segments may be hinged to thesupport member or may be constructed so as to be flexible in nature. Inorder to secure the positive expansion of these shroud segments thehydraulic force of drilling mud at the primary nozzle is employed toforce extension of the shroud segments. In one form of the inventionthis hydraulic force is used to apply a cam action to the segmentedshroud while in another form of the invention the expansive force of asleeve member is employed to force extension of the shroud. It isapparent that the principles of this invention may be modified in manyrespects in providing desirable forms of expansible shrouds for pelletimpact drills.

What is claimed is:

1. A drilling apparatus comprising in combination: a tubular supportmember, a plurality of circumferentially arranged shroud segments heldby said support member in flexible relation thereto and extending belowsaid support member in a manner defining an open-bottom shroud adaptedto maintain a plurality of pellets in captive circulation therewithin, afirst nozzle element supported by said tubular member adjacent the lowertermination thereof and adapted to eject therefrom a high velocitystream of fluid, a second nozzle element supported below said firstnozzle element in spaced concentric relation therewith, said secondnozzle element being spaced from said shroud elements and from saidfirst nozzle element to provide for upward passage of pellets betweensaid second nozzle element and said shroud and for entry of pellets intothe top of said second nozzle, means biasing said shroud segmentsinwardly with respect to the vertical axis of the apparatus and meansadapted to force said shroud segments outwardly in opposition to saidbias when fluid pressure is built up within said tubular support as aresult of forcing fluid out of said support through said first nozzle.

2. Drilling apparatus as defined by claim 5 including inward extensionsfixed to said shroud segments, said first nozzle element being slidablyheld Within said tubular member and supported on said extensions, saidextensions being characterized by a downward and inward taper wherebypressure applied downwardly to said first nozzle causes extension ofsaid shroud segments.

3. Apparatus as defined by claim 1 including a flexible sleeve elementpositioned within said tubular support above said first nozzle elementwith a portion of said sleeve engaging the upper ends of said shroudsegments in a manner forcing said segments outwardly upon said build-upof fluid pressure within said tubular support.

4. Apparatus as defined by claim 1 including notches in each of saidshroud segments collectively defining an external circumferential recessand a ring fitting loosely in said recess when said segments are intheir inward position, and tightly when said segments are extended,whereby to limit the outward extension of said segments.

References Cited in the file of this patent UNITED STATES PATENTS1,452,734 Griesche Apr. 24, 1923 1,502,851 Gale July 29, 1924 2,233,260Hawthorne Feb. 25, 1941 2,602,642 Baker July 8, 1952

1. A DRILLING APPARATUS COMPRISING IN COMBINATION: A TUBULAR SUPPORTMEMBER, A PLURALITY OF CIRCUMFERENTIALLY ARRANGED SHROUD SEGMENTS HELDBY SAID SUPPORT MEMBER IN FLEXIBLE RELATION THERETO AND EXTENDING BELOWSAID SUPPORT MEMBER IN A MANNER DEFINING AN OPEN-BOTTOM SHROUD ADAPTEDTO MAINTAIN A PLURALITY OF PELLETS IN CAPTIVE CIRCULATION THEREWITHIN, AFIRST NOZZLE ELEMENT SUPPORTED BY SAID TUBULAR MEMBER ADJACENT THE LOWERTERMINATION THEREOF AND ADAPTED TO EJECT THEREFROM A HIGH VELOCITYSTREAM OF FLUID, A SECOND NOZZLE ELEMENT SUPPORTED BELOW SAID FIRSTNOZZLE ELEMENT IN SPACED CONCENTRIC RELATION THEREWITH, SAID SECONDNOZZLE ELEMENT BEING SPACED FROM SAID SHROUD ELEMENTS AND FROM SAIDFIRST NOZZLE ELEMENT TO PROVIDE FOR UPWARD PASSAGE OF PELLETS BETWEENSAID SECOND NOZZLE ELEMENT AND SAID SHROUD AND FOR ENTRY OF PELLETS INTOTHE TOP OF SAID SECOND NOZZLE, MEANS BIASING SAID